Device for actuating an electromagnetically controlled injector

ABSTRACT

Actuating device for an injector having a chamber the opening of which for injection is caused by the pressure of the fuel supplied to the chamber. The actuating device comprises a slidable closure member of fuel valve means which is shifted by electromagnetic means. Two opposed faces are provided on opposed ends of the closure member which respectively co-operate with two opposed seats on a body surrounding the closure member. The two faces and two seats define in the body a first end chamber, a second end chamber and a third chamber. Passage means put the first chamber in communication with a source of fuel under pressure, the second chamber in communication with a source of pressure lower than the pressure of the fuel and the third chamber in communication with the chamber of the valve.

United States Patent 1191 Re neault et al. 11 A r. 9 1974 DEVICE FOR ACTUATING AN 3,680,782 8/1972 Monpetit et al. 239/96 ELECTROMAGNETICALLY CONTROLLED INJECTOR Primary Examiner-M. Henson Wood, Jr.

Assistant ExaminerMichael Y. Mar l 1 [75] Inventors xili t i v l'lifi fp ii ihf? Mme/9 n :2 wt P sn 1.W s

Franc e Mathis [73] Assignee: Automobiles Peugeot, Paris, France [57] S C 22 F'ld: 1131973 1 l e y Actuating device for an m ector having a chamber the PP 378,906 opening of which for injection is caused by the pres- Related US Application Data sure of the fuel supplied to the chamber. The actuat- [63] C t f S N 266 235 J 26 ing device comprises a slidable closure memberof fuel g 0 une valve means which is shifted by. electromagnetic y means. Two opposed faces are provided on opposed 1 ends of the closure member which respectively co- [3O] Forelgn Apphcanon Pnomy Data operate with two opposed seats on a body surrounding July 8, 1971 France 71.266235 the closure member The two faces and two seats fine in the body a first end chamber, a second end [52] US. Cl 239/96, 23953352335213: chamber and a third Chainben Passage means put the IIPt. Cl. first chamber in communication with a Source of fuel [58] new of Search 3 under pressure, the second chamber in communication with a source of pressure lower than the pressure of the fuel and the thirdchamber in communication [56] uNlTE g gzzggs gziENTs with the chamber of the valve. 8,481,542 12/1969 Huber 239/585 x 13 Claims Drawing Figures DEVICE FOR ACTUATING AN ELECTROMAGNETICALLY CONTROLLED INJECTOR This application is a Continuation-In-Part of applicationSer. No. 266,235, filed June 26, 1972.

The present invention relates to internal combustion engines of the fuel injectiontype and more particularly concerns injecting devices in which the injectors are actuated partly by electrical or electronic means.

The latter expression is intended to mean that the device controlling the injection comprises a calculator which, as a function of a number of parameters, furnishes control or command signals to electromagnets which directly or indirectly actuate the injector. Usually, these injectors comprise a needle received in an injector holder in which are also incorporated the actuating means which raise the needle from its seat and consequently control the injection.

Generally, these means may be put into two categories: in thefirst category theneedle of the injector is raised directly by the action of a magnetic device the moving part of which is constituted by the needle. This arrangement has the drawback of requiring large magnetic forces since it is necessary to, overcome the force of the return spring returning the needle and possibly the hydraulic pressure exerted by the fuel on the rear part of the needle.

In a second category, the needle of l the injector is raised by the action of the pressure of the fuel prevail ing in an annular chamber located in the vicinity of the point of the needle and partly defined by the seat for the latter, this chamber being put in communication with or cut off from the pressure by a valve which is ac tuated by an electromagnetic device. This valve can be constituted by a ball valve or a cylindrical slide valve having bearing portions which stop or allow the communication between conduits which communicate laterally with the interior of the body of this valve. This mode of actuating also has drawbacks. Indeed, the ball valve requires an electromagnetic device of some power in order to overcome the pressure of the liquid and moreover it has an operating time which is a function of the pressure, which does not permit varying this pressure in the desired manner for reducing the duration of injection when the engine running speed increases so as to avoid spreading the injection over an excessively large angle.

The slide valve can be balanced but this requires a relatively long stroke which results in excessively slow opening and closing of the needle valve, a drawback which can be overcome only partly by providing an electromagnetic device which is powerful enough to overcome the forces of inertia.

Thus the known devices all have serious drawbacks and an object of the invention is to provide an actuating device for an injector which overcomes these drawbacks.

The invention provides an actuating device for an injector comprising a chamber which is defined partly by a seat co-operating with the moving element of the injector and which surrounds this moving element and may be selectively put under pressure by way of a valve having a sliding or closure member, the valve being controlled by an electromagnet, wherein the closure member is subjected on both ends to the same force of pressure, the closure member and the bodyin which it is received having respectively two opposite active faces and two opposite seats defining a centre chamber and two lateral chambers which chambers are respectively connected to the injector, to a source of fuel under pressure, such as an injection pump, and to an enclosure in which prevails a pressure lower than the pressure of said source, for example atmospheric pressure. a

With suchan arrangement, the closure member is perfectly balanced and requires a very short travel which results in a number of advantages.

According to a modification of .the actuating device, the closure member is made in two parts which bear axially against each other, each of these parts having its own guide stem and an active face which cooperates with the corresponding seat.

In this way each closure member part is independent of the other and any possible lack of alignment of the bores receiving these parts will have no adverse effect on the operation of the closure member.

Further features and advantages of the invention will be apparent from the ensuing description with reference to the accompanying drawings in which:

FIG. 1 is a sectional view of an injector and an injector holder in which is incorporated the device accord-- ing to the invention;

FIG. 2 is a detail sectional view, to an enlarged scale, of the distributor valve employed in accordance with the invention;

FIG. 3 is-a detail view to an enlarged scale of the distributor valve in which the closure member is in two parts, the bores receiving the two parts being shown radially offset from each other, and I FIG. 4 is a detail view similar to FIG. 3 in which the two bores receiving the two parts of the closure member are angularly out of alignment.

FIG. 1 shows an injector holder 1 v in which is mounted an injector comprising an injector head 2 and a needle 3. The injector is fixed to the injector holder by a screwthreaded collar 4 and the needle 3 is biased by a spring 5 which bears against a plug 6 to which a connector 7 is connected. The latter is connected to an enclosure in which prevails a pressure in the neighbourhood of atmospheric pressure.

The injector head 2 has at its end an injection orifice 8 and defines a seat 9 at the end of the needle 3. An annular chamber 10 is formed in the head of the injector around the needle and in the vicinity of the seat 9 and a-conduit 11 connected to a source of fuel under pressure, in the present case the fuel injection pump, opens into this annular chamber 10.

The injector holder 1 has a lateral extension portion 1a in which are received a distributing valve 12 and an electromagnet 13 which is adapted to actuate this valve and will be described in more detail hereinafter. This lateral projecting portion is connected by a connector 1b to the delivery side of the injection pump (not shown).

The distributor valve 12 (FIG. 2) comprises a composite body 14, 15, 16, 17 defining two bores 18, 19 of the same diameter and a centre chamber 20 of larger diameter. The centre chamber is connected by way of a passageway'2l, 22, 23 to the conduit 11 leading to the annular chamber 10. The chamber 18, on the left as viewed in the drawing, is connected to the delivery side of the injection pump, the chamber 19, on the right as viewed in the drawing, being put under pressure by way of a lateral passage 24 and a conduit 25. Slidably mounted in the body of the distributing valve is a slide member 26 having in the following order, starting from the left as viewed in the drawing: a grooved guide stem 27 slidable in the bore 18, an enlarged centre portion 28 defining two active faces 29 and 30 constituting valve closure members adapted to co-operate with two seats 31, 32 defined by the body, and then a solid guide stem 33 slidably mounted in the bore 19. In the chosen embodiment, the faces 29, 30 and the seats 31, 32 have frustoconical shapes with slightly different included angles.

A conduit 34 extends from the chamber 35 defined between the valve closure member 30 and the solid guide stem 33, this conduit being connected to the upper part of the injector holder. Provided between the wall of the injector holder which constitutes the end of the bore 19 and the guide stem 33 of the slide member is a spring 36 which biases the slide member to its position shown inYFIG. 2.

The electromagnet 13 comprises a coil 37 and a moving part 38constituted by a needle which bears by its right end, as viewed in the drawing, against the adjacent end face of the slide member 26.

The actuating device operates in the following manner:

The fuel delivered under pressure by the injection pumpenters the assembly by way of the connector 1b. This fuel under pressure flows through the electromagnet and reaches the chamber 18 by way of the grooves or flutes of the slide member 26 and also reaches the chamber 19 by way of the passage 24 and the conduit 25 Thus it can be seen that the member 26 is subjected to balanced hydraulic pressures and that only the spring 36 is operative for shifting the valve closure member 30 from its seat 32 and apply the valve closure member 29 against its seat 31. In this position of the slide member, the annular chamber communicates with the atmosphere by way of the conduits 11, 23, 22, 21, the chambers 20,35 and the conduit 34.

When the electromagnet 13 is energized by a signal from an electronic-calculator (not shown), the moving part 38 urges the slide member 26 to the right as viewed in the drawing and compresses the spring 36. The communication between the chamber and the exhaust is then cutoff whereas the pressure of injection prevails in the chamber 20 and is communicated to the annular chamber 10 by way of the conduits 21, 22, 23 and 11. The needle 3 of the injector is then urged upwardly in opposition to the action of its return spring 5 and the injection occurs through the orifice 8 until the coil 37 of the electromagnet is no longer supplied with current.

When the slide member 26 is shifted by the electromagnet, the section of the passage thus provided for the fuel is large even if the travel of the slide member is small since this area is disposed around the whole of the According to another feature of the invention, there is inserted in the conduit 11 a jet 39 which acts on the flow of the fuel during the injection time. Consequently, as a result of this jet, the amount of fuel in- 5 jected is unaffected by a possible soiling of the nose of periphery of the closure member. Further, in view of the fact that the slide member is subjected on both end faces to balanced hydraulic forces and its mass is very small, the power that the electromagmet must develop is also very small while it still ensures the required char- 1 acteristics of a rapid opening and closure. This electromagnet can consequently be of small size and consume a small amount of current so that it is also possible to reduce the characteristics of the electronic components constituting the power stage of the calculator.

the injector whose passage section may be chosen much greater than that of the jet 39.

Further, although it has been proposed to apply on the two end faces of the slide member 26 the pressure of the fuel supplied by the injection pump, an equivalent result may be obtained by subjecting these two end faces to a different pressure which may be, for example, the discharge pressure which is in the neighbourhood of atmosphere pressure. The necessary transformation of the circuit will be obvious to one skilled in the art and therefore has not been illustrated or described. Likewise, the configuration of the injector proper is not criticle and the invention is applicable to both teat injectors and orifice injectors.

In the modification of theactuating device shown in FIGS. 3 and 4, the distributor valve D, mounted in the injector holder extension portion la comprises a composite body 101, 102, 103, 104. Each of the parts 101 and 102 defines a bore 105 and 106. This body thus defines three chambers:

a centre chamber 107 having a diameter exceeding that of the bores 105, 106;

a chamber 108 located on the left side, as viewed in the drawing;

a chamber 109 located on the right side, as viewed in the drawing.

Chamber 107 is connected, in the presentlydescribed embodiment, to the chamber 10 of the injector by a conduit 140, chamber 108 is connected to the source of fuel under pressure as in the embodiment shown in FIGS. 1 and 2 and chamber 109 is connected, in the presently described embodiment, to the enclosure in which prevails a pressure at about atmospheric pressure, by a conduit 141.

In the composite body just described there are mounted two closure or slide members, constituting a composite closure or slide member, namely closure member 110 and closure member 120, the member 1 10 having a grooved or fluted guide stem 111 slidable in the bore 105 and a head 112 of larger diameter defining a frustoconical active face 113 acting as a valve member and adapted to co-operate with a seal 114 which is also frustoconical and formed in the part 102 of the composite body.

The closure member has a guide stem 121 slidable in the bore 106 and an enlarged head 122 which defines an active face 123 co-operating with a seat 124 formed in the part 104 of the body. The face 123 and seat 124 are also frustoconical.

The frustoconical faces 113, 123 and seats 114, 124 may have slightly different included angles.

At its left end (as viewed in the drawing), the closure member 1 l0 bears against the point of the moving part 38 of the electromagnet 13 and this member 110 is shifted by the electromagnet in the same way as in the embodiment shown in FIGS. 1 and 2. The right end of closure member 110 is in axial abutting relation to the left end of the closure member 121 which has its right end engaged with a return spring 131 which biases the member 121 to the left and thereby maintains the adjacent faces 115, 125 of the closure members 110 and 121 in contact and biases the composite closure memher 1 10, 121 against the point of the moving part 38 of the electromagnet.

As can be seen in FIG. 3, in view of the fact that the two bores 105, 106 are formed in different parts of the composite body, their axes XX, Y--Y, while being parallel, could be slightly out of alignment (shown in an exaggerated manner in FIG. 3) and this would be a disadvantage if the closure member were in one piece and defined both the active face 113 and the active face 123. Indeed, the seal between these faces and their seats would not be achieved correctly in both directions of movement of the closure member and the distributor valve would not perform its function perfectly well.

Now, according to the presently-described modification of the closure member, the closure members 110 and 120 are independent from each other and have their own guide means and their own active face. Thus the radial offset between the axes X-X and Y-Y can be accommodate by the fact that the end faces 1 and 125 are radially relatively slidable and the axes Xand and Y-Y are free to takeup their respective positions.

In FIG; 4, the same distributor valve is shown in the case where the axes XX and Y-Y of the bores 105 and 106 formed in the parts 102 and 104 of the composite body are angularly out of alignment and not radially offset (the angular lack of alignment has been exaggerated). Here again, it can be seen that the fact of making the closure member intwo parts 110, 120 enables this lack of alignment to be accommodated with no inconvenience, the end faces 115 and 125 being in contact with each other on their edges and not throughout their area. This type of contact has no adverse effect on the correct operation of the distributor valve since it is merely sufficient to ensure contact in a given zone. Note, moreover, that this lack of angular alignment would be infinitely small in practice.

The advantages of this modification to the closure or slide member of the distributor valve will be clear from the foregoing description. They concern, on one hand, the very construction of the distributor valve the machining and assembly of which no longer need to be so precise, which considerably reduces production costs, and on the other hand, the operation of the distributor valve which becomes more precise and more reliable. The latter advantage in particular enables the distributor valve to be used for actuating fuel injectors in which pressures of several hundred bars are set up and in which the response time must be very short.

A modification may be made in the shape of the faces 115 and 125. Instead of being both planar as shown in FIGS. 3 and 4, one of them could be so shaped as to result in a point contact with the face of the other closure member. For example, the closure member 110 could have a conical end face instead of the planar end face 115, the point of the cone contacting the face 125. This arrangement is above all of interest in the event that the axes XX and Y-Y are angularly out of alignment as shown in FIG. 4.

It will be understood that the distributor valve shown in FIGS. 3 and 4 may be modified but still incorporate the advantages of the composite closure member 110,120. For example, the closure members 110 and 120 may be reversed in position in the body 101,102,103, 104 so that the point of member 38 acts on the end of closure member 120 instead of closure member .100, the chamber 109 being defined by the part 102 instead of the part 104 and the chamber 108 being defined by the part 104. In this case the conduit 141 would traverse the part 103 and part 102 to communicate with the chamber 109 in its new location on the left side of chamber 107 (as viewed in the drawing). Further, the conduit need not lead to a chamber of an injector such as chamber 10 between the seat 9 and the enlarged part of the needle 3. For example, it could lead to a chamber of a fuel injector at the end of the injector needle opposed to the end co-operating with the seat.

Having now described our invention what we claim as new and desire to secure by Letters Patent is:

1. An actuating device for an injector having means defining a first chamber, a movable valve member cooperative with an injector outlet orifice and partly defining the chamber so as to be responsive to change in pressure in the'chamber; the actuating device comprising distributor valve means having means defining a body, means defining a bore in the body, closure means slidable in the bore, means for subjecting opposite ends of the closure means to identical pressure forces, two opposite sealing faces on the closure means, two opposed seats on the body for co-operation with the sealing faces, electromagnetic means combined with the closure means for shifting the closure means in the bore between a position in which a first of said faces sealingly engages a first of said seats and a position in which a second of said faces sealingly engages a second of said seats, the closure means defining with the body a second chamber when said first face and first seat are in engagement, the closure means defining with the body a third chamber when said second face and second seat are in engagement, a fourth chamber in the body capable of communicating with the second chamber when the first face and first seat are separated from each other, and capable of communicating with the third chamber when the second face and second seat are separated from each other, passage means for putting the second chamber in communication with a source of fuel under pressure, passage means for putting the third chamber in communication with a source pressure lower than the pressure of said fuel and passage means for putting the fourth chamber in communication with the first chamber.

2. An actuating device for an injector having means defining a first chamber, a movable valve member cooperative with an injector outlet orifice and partly defining the chamber so as to be responsive to change in pressure in the chamber; the actuatingdevice comprising distributor valve means having means defining a body, means defining a first end bore and a second end bore and a third bore in the body, the third bore being intermediate the first bore and second bore and having a diameter larger than the diameter of the first bore and second bore, the three bores being coaxial, closure means slidable in the first bore and second bore, means for subjecting opposite ends of the closure means to identical pressure forces, means defining an enlargement on the closure means, the enlargement defining two opposite frustoconical sealing faces, a first guide stem portion extending in one direction from the enlargement and slidable in the first bore a second guide stem portion extending from the enlargement and slidable in the second bore, two opposed frustoconical seats on the body for co-operation with the sealing faces, one of the seats being interposed between the first bore and third bore and the other of the seats being interposed between the second bore and the third bore, electromagnetic means combined with the closure means for shifting the closure means in the bores between a position in which a first of said faces sealingly engages a first of said seats and a position in which a second of said faces sealingly engages a second of said seats, the closure means defining with the first bore a second chamber with said first face and first seat are in engagement, the closure means defining with the second bore a third chamber within said second face and second seat are in engagement, the third bore defining a fourth chamber in the body which is capable of communicating with the second chamber when the first face and first seat are separated from each other and capable of communicating with the third chamber when the second face and second seat are separated from each other, passage means for putting the second chamber in communication with a source of fuel under pressure, passage means for putting the third chamber. in communication with a source of pressure lower than the pressure of said fuel, and passage means for putting the fourth chamber in communication with said first chamber.

3. The device of claim 2, wherein said identical pressures correspond to the pressure of said fuel of said source.

4. The device of claim 2, comprising groove means on said first guide stem portion which constitute part of said passage means for putting the second chamber in communication with said source of fuel, and a by-pass passageway for permitting the passage of said fuel under pressure to the second bore at the end of the second guide stem portion.

5. The device of claim 4, wherein the second guide stem portion includes a smooth bearing portion which is in engagement with the second bore and defines with the second face of the closure means and the second bore the third chamber.

6. The device of claim 1, comprising resiliently yieldable means combined with the closure means for biasing the closure means to a position in which the fourth chamber communicates with the third chamber.

7. The device of claim 1, comprising a jet inserted in the passage means for connecting the fourth chamber to the first chamber.

8. The device of claim 2, wherein the sealing faces and the seats have different tapers.

9. An actuating device for an injector having means defining a first chamber, a movable valve member cooperative with an injector outlet surface and partly defining the chamber so as to be responsive to change in pressure in the chamber; the actuating device comprising distributor valve means having means defining a body, said body comprising a first body member and a second body member, means defining a first bore in the first body member and a second bore in the second body member, the first and second bores being coaxial, closure means comprising a first closure member slidable in the first bore and a second closure member slidable in the second bore, the two closure members being in engagement with each other at first ends of the closure members, means for subjecting second ends of the closure members opposed to said first ends to identical pressure forces axially of the bores, a first sealing face on the first closure member, a second sealing face on the second closure member, a first seat on the first body member and a second seat on the second body member for cooperation with the first sealing face and second sealing face respectively, electromagnetic means combined with the closure means for shifting the closure means in the bores between a position in which the first sealing face sealingly engages the first seat and a position in which the second sealing face sealingly engages the second seat, the first closure member defining with the first body a second chamber when said first face and first seat are in engagement, the second closure member defining with the second body member a third chamber when said second face and second seat are in engagement, a fourth chamber in the body capable of communicating with the second chamber when the first face and first seats are separated from each other and capable of communicating with the third chamber when the second face and second seat are separated from each other, passage means for putting the second chamber in communication with a source of fuel under pressure, passage means for putting the third chamber in communication with a source of pressure lower than the pressure of said fuel, and passage means for putting the fourth chamber in communication with the first chamber.

10. The device of claim 9, wherein the electromagnetic means comprise a thrust member adapted and arranged to exert an axial thrust on the first closure member upon energization of the electromagnetic means and spring means are interposed axially between the second closure member and the second body for biasing the two closure members into engagement with each other and the first closure member into engagement with the thrust member of the electromagnetic means. i

11. The device of claim 9, wherein said sealing faces and seats are annular and frustoconical.

12. Combination comprising an injector holder having a lateral extension portion; an injector held in the injector holder and comprising means defining a first chamber, a seat defined by a portion of the first chamber, a movable valve member of the injector disposed in the first chamber and co-operative with the seat; and an actuating device for the injector, the actuating device being disposed in the extension portion and comprising distributor valve means having means defining a body, means defining a bore in the body, closure means slidable in the bore, means for subjecting opposite ends of the closure means to identical pressure forces, two opposite sealing faces on the closure means, two opposed seats on the body for co-operation with the sealing faces, electromagnetic means combined with the closure means for shifting the closure means in the bore between a position in which a first of said faces sealingly engages a first of said seats and a position in which a second of said faces sealingly engages a second of said seats, the closure means defining with the body a second chamber when said first face and first seat are in engagement, the closure means defining with the body a third chamber when said second face and second seat are in engagement, a fourth chamber in the body capable of communicating with the second chamber when the first face and first seat are separated from each other and capable of communicating with the third chamber when the second face and second seat are separated from each other, passage means for putting the second chamber in communication with a source of fuel under pressure, passage means for putting the third chamber in communication with a source of pressure lower than the pressure of said fuel, and passage means for putting the fourth chamber in communication with the first chamber.

13. The combination of claim 12, wherein the means defining the body comprise a first body member defining a first portion of said bore and a second body member defining a second portion of said bore and the cloand second body member respectively.

a UNITED STATES PATENT OFFICE CERTIFICATE OF "CORRECTION Patent No. 3, 802.626 Dated April 9, 1974 t fl Marcel Reqneault and Jean Perez pears in the above-identified patent It is certified that error ap d as shown below:

and that said Letters Patent are hereby correcte Foreign Application Priority Data should read a5 follows:

July 8, 1971 France 71 25 044 Signecland sealed this 1st day of October 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents USCOMM-DC 60376-1 69 & \LS, GOVERNMENT PRINTING OFFICE: 969 O36 6-33l FORM eo-xoso (10-69) 

1. An actuating device for an injector having means defining a first chamber, a movable valve member co-operative with an injector outlet orifice and partly defining the chamber so as to be responsive to change in pressure in the chamber; the actuating device comprising distributor valve means having means defining a body, means defining a bore in the body, closure means slidable in the bore, means for subjecting opposite ends of the closure means to identical pressure forces, two opposite sealing faces on the closure means, two opposed seats on the body for co-operation with the sealing faces, electromagnetic means combined with the closure means for shifting the closure means in the bore between a position in which a first of said faces sealingly engages a first of said seats and a position in which a second of said faces sealingly engages a second of said seats, the closure means defining with the body a second chamber when said first face and first seat are in engagement, the closure means defining with the body a third chamber wHen said second face and second seat are in engagement, a fourth chamber in the body capable of communicating with the second chamber when the first face and first seat are separated from each other, and capable of communicating with the third chamber when the second face and second seat are separated from each other, passage means for putting the second chamber in communication with a source of fuel under pressure, passage means for putting the third chamber in communication with a source pressure lower than the pressure of said fuel and passage means for putting the fourth chamber in communication with the first chamber.
 2. An actuating device for an injector having means defining a first chamber, a movable valve member co-operative with an injector outlet orifice and partly defining the chamber so as to be responsive to change in pressure in the chamber; the actuating device comprising distributor valve means having means defining a body, means defining a first end bore and a second end bore and a third bore in the body, the third bore being intermediate the first bore and second bore and having a diameter larger than the diameter of the first bore and second bore, the three bores being coaxial, closure means slidable in the first bore and second bore, means for subjecting opposite ends of the closure means to identical pressure forces, means defining an enlargement on the closure means, the enlargement defining two opposite frustoconical sealing faces, a first guide stem portion extending in one direction from the enlargement and slidable in the first bore a second guide stem portion extending from the enlargement and slidable in the second bore, two opposed frustoconical seats on the body for co-operation with the sealing faces, one of the seats being interposed between the first bore and third bore and the other of the seats being interposed between the second bore and the third bore, electromagnetic means combined with the closure means for shifting the closure means in the bores between a position in which a first of said faces sealingly engages a first of said seats and a position in which a second of said faces sealingly engages a second of said seats, the closure means defining with the first bore a second chamber with said first face and first seat are in engagement, the closure means defining with the second bore a third chamber within said second face and second seat are in engagement, the third bore defining a fourth chamber in the body which is capable of communicating with the second chamber when the first face and first seat are separated from each other and capable of communicating with the third chamber when the second face and second seat are separated from each other, passage means for putting the second chamber in communication with a source of fuel under pressure, passage means for putting the third chamber in communication with a source of pressure lower than the pressure of said fuel, and passage means for putting the fourth chamber in communication with said first chamber.
 3. The device of claim 2, wherein said identical pressures correspond to the pressure of said fuel of said source.
 4. The device of claim 2, comprising groove means on said first guide stem portion which constitute part of said passage means for putting the second chamber in communication with said source of fuel, and a by-pass passageway for permitting the passage of said fuel under pressure to the second bore at the end of the second guide stem portion.
 5. The device of claim 4, wherein the second guide stem portion includes a smooth bearing portion which is in engagement with the second bore and defines with the second face of the closure means and the second bore the third chamber.
 6. The device of claim 1, comprising resiliently yieldable means combined with the closure means for biasing the closure means to a position in which the fourth chamber communicates with the third chamber.
 7. The device of claim 1, comprising a jet inserted in the passage means for conneCting the fourth chamber to the first chamber.
 8. The device of claim 2, wherein the sealing faces and the seats have different tapers.
 9. An actuating device for an injector having means defining a first chamber, a movable valve member co-operative with an injector outlet surface and partly defining the chamber so as to be responsive to change in pressure in the chamber; the actuating device comprising distributor valve means having means defining a body, said body comprising a first body member and a second body member, means defining a first bore in the first body member and a second bore in the second body member, the first and second bores being coaxial, closure means comprising a first closure member slidable in the first bore and a second closure member slidable in the second bore, the two closure members being in engagement with each other at first ends of the closure members, means for subjecting second ends of the closure members opposed to said first ends to identical pressure forces axially of the bores, a first sealing face on the first closure member, a second sealing face on the second closure member, a first seat on the first body member and a second seat on the second body member for co-operation with the first sealing face and second sealing face respectively, electromagnetic means combined with the closure means for shifting the closure means in the bores between a position in which the first sealing face sealingly engages the first seat and a position in which the second sealing face sealingly engages the second seat, the first closure member defining with the first body a second chamber when said first face and first seat are in engagement, the second closure member defining with the second body member a third chamber when said second face and second seat are in engagement, a fourth chamber in the body capable of communicating with the second chamber when the first face and first seats are separated from each other and capable of communicating with the third chamber when the second face and second seat are separated from each other, passage means for putting the second chamber in communication with a source of fuel under pressure, passage means for putting the third chamber in communication with a source of pressure lower than the pressure of said fuel, and passage means for putting the fourth chamber in communication with the first chamber.
 10. The device of claim 9, wherein the electromagnetic means comprise a thrust member adapted and arranged to exert an axial thrust on the first closure member upon energization of the electromagnetic means and spring means are interposed axially between the second closure member and the second body for biasing the two closure members into engagement with each other and the first closure member into engagement with the thrust member of the electromagnetic means.
 11. The device of claim 9, wherein said sealing faces and seats are annular and frustoconical.
 12. Combination comprising an injector holder having a lateral extension portion; an injector held in the injector holder and comprising means defining a first chamber, a seat defined by a portion of the first chamber, a movable valve member of the injector disposed in the first chamber and co-operative with the seat; and an actuating device for the injector, the actuating device being disposed in the extension portion and comprising distributor valve means having means defining a body, means defining a bore in the body, closure means slidable in the bore, means for subjecting opposite ends of the closure means to identical pressure forces, two opposite sealing faces on the closure means, two opposed seats on the body for co-operation with the sealing faces, electromagnetic means combined with the closure means for shifting the closure means in the bore between a position in which a first of said faces sealingly engages a first of said seats and a position in which a second of said faces sealingly engages a second of said seats, the closure means defiNing with the body a second chamber when said first face and first seat are in engagement, the closure means defining with the body a third chamber when said second face and second seat are in engagement, a fourth chamber in the body capable of communicating with the second chamber when the first face and first seat are separated from each other and capable of communicating with the third chamber when the second face and second seat are separated from each other, passage means for putting the second chamber in communication with a source of fuel under pressure, passage means for putting the third chamber in communication with a source of pressure lower than the pressure of said fuel, and passage means for putting the fourth chamber in communication with the first chamber.
 13. The combination of claim 12, wherein the means defining the body comprise a first body member defining a first portion of said bore and a second body member defining a second portion of said bore and the closure means comprise a first closure member slidable in the first bore portion and a second closure member slidable in the second bore portion, the closure members being relatively movable, the first sealing face and second sealing face being on the first closure member and second closure member respectively and the first seat and second seat being on the first body member and second body member respectively. 